1. Field of the Invention
This invention generally relates to semiconductor and integrated circuit (IC) fabrication and, more particularly, to a process for fabricating high aspect-ratio submicron silicon (Si) tubes.
2. Description of the Related Art
Si substrates with submicron to nano-scale sized structures are of increasing interest due to their physical properties and their potential for use in new nanodevices. For example, small feature sizes would be useful in nanowire field effect transistors, nano-Si photonics, nano-Si substrates for III-V and SiC light emitting diode (LED) devices, high power, and microelectromechanical system (MEMS) device applications. Comprehensive studies on the vapor-liquid-solid (VLS) growth of whiskers of silicon and other materials, with sizes down to the 100 nanometer (nm) began in the 1960's and 1970's. However, the fabrication of structures with a defined radius, position, length, and therefore, technological application proved to be elusive at that time.
In more recent years, remarkable progress has been achieved. Several growth concepts have been developed for semiconductors, ceramics, and metals, permitting the fabrication of whiskers with diameters of 100 nm and a length of several micrometers. Silicon whiskers are normally grown by chemical vapor deposition (CVD), gas-source molecular-beam epitaxy (GS-MBE), and recently developed electrochemical wet etching processes. CVD and GS-MBE are very expensive processes, however, and it has proven difficult to control the nanowire position, distribution, and orientation. Further, it is difficult to remove the catalyst needed to promote the nanowire growth. The electrochemical wet etching processes requires the use of Si wafers with a very low resistivity (typically <0.01 Ωcm), which limits the process applications.
It would be advantageous if processes existed for fabricating submicron and nano-scale Si structures with controlled features.
It would be advantageous if Si nanotubes could be fabricated using a process to control the nanotube height, diameter, and density.